1. Field of the Invention
The present invention relates to a centrifuge instrument having a system for automatically identifying a rotor introduced thereinto.
2. Description of the Prior Art
A centrifuge instrument is a device adapted to expose a liquid sample carried in a rotating member, called a rotor, to a centrifugal force field. The centrifuge instrument includes a drive shaft, or spindle, adapted to receive any one of a predetermined plurality of rotors. It is important to correctly ascertain the identity of a particular rotor being used in the instrument at any given time. Such rotor identity information is important, among other reasons, for automatically controlling acceleration and deceleration times and for controlling the temperature or other parameters related to the particular separation being effected. Perhaps more importantly rotor identification is vital to insure that the particular rotor being used is not rotated to a speed that would cause rotor disintegration at an energy level high enough to breach the containment system of the instrument.
Presently rotor identification may be performed manually be requiring the operator of the instrument to introduce information via the control panel regarding the identity of the particular rotor being utilized. This system is open to inadvertent error or deliberate misrepresentation by the operator and thus cannot be relied upon for providing rotor identification information if the same is being used in connection with any safety-related consideration.
Automatic systems for rotor identification are available. Exemplary of such systems are those shown in U.S. Pat. No. 4,551,715 (Durbin) and U.S. Pat. No. 4,601,696 (Kamm). These systems utilize some form of coding elements usually disposed on the undersurface of the rotor. The coding elements are read by an appropriate optical or magnetic detector mounted in an operative location in the instrument. These systems share the disadvantage that the detector element, due to its location within the instrument, may be subject to corrosion which would vitiate its ability to accurately detect the coding elements provided on the rotor. Moreover such a system would be inapplicable in ascertaining the identity of rotors not equipped with the appropriate coding elements. Thus these identification systems would be unable to identify a significant population of rotors unless those rotors were retrofit with the appropriate coding elements. Furthermore retrofitting carries with it the risk of accidental or deliberate mismarking of the rotor and for this reason shares the same disadvantages as discussed above.
A rotor identification system relying on the interruption of a beam of light from a source to a detector is disclosed in U.S. Pat. No. 4,450,391 (Hara).
U.S. Pat. No. 4,827,197 (Giebeler) discloses a rotor identification system based on the inertia of the rotor when the rotor is used in what is believed to be an evacuated chamber. Such a system may be applicable for use in a nonevacuated or partially evacuated chamber so long as the inertia measurement is made at an angular velocity which is sufficiently low so that windage effects are negligible. This system would appear to become unreliable when windage effects become dominant.
An ultrasonic rotor recognition system is disclosed and claimed in copending application Ser. No. 07/363,907, filed May 18, 1989, and now U.S. Pat. No. 5,037,371 based on international application PCT/US87/03221 (Romanauskas), and now International Publication No. W088/0420, assigned to the assignee of the present invention.